Weird sound

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Jul 12, 2008
Hey guys I could use some help. My 40 has developed a sound that I'm having a dickens of a time tracking down. It's an intermittent sound that starts at speed with a tick tick tick kind of sound...doesn't seem to be speed related. As I slow down it goes from a ticking sound to more of a clunk clunk...again not 100% speed related (aka doesn't slow when I do). Happens mostly in 2wd although I did make it happen once in 4wd. Best I can tell it seems to be front end. There is no unusual feel to the truck, nor any shaking when it happens. Any ideas?

The truck is a 75 with the 2f/4sp. Stock course spline front with warn hubs. 39k original miles...non restored (survivor). The drivers hub has become a little finicky as well (won't always turn easy) so I don't know if that related.

The major issue is I can't make it start as a slow enough speed to be next to I can't seem to track it down. Happens with clutch in or out, and doesn't matter if I'm braking or not.
Rebuild that hub and see if it stops. The kits are cheap enough. ;)

Can you tell if the noise is coming from one side or the other?
Does the noise increase on hard acceleration?

Other than the speed relation I'd venture a guess at a broken tooth on the ring gear. Sometimes they barely make any noise, if any, when only 1 tooth is missing, and on hard acceleration you would be stressing the teeth on either side more than normal causing the clunking sound.

Again, this is just an idea for where to look, not a diagnosis at all. Though, sometimes I get lucky.
On power or off doesn't matter. If I coast down it makes the sound too. If I accelerate it does not get any worse. Seems maybe pass side (drivers hubis sticky) but when it's clunking it's midline or to the drivers side. I was thinking broken teeth, was gonna pull the drain on the diff and check the old but didn't have any to replace so I haven't yet. I tried it again and could not make it do the sound in 4wd or with both hubs locked...but that may have just been because I didn't give it enough time.
not a professional mechanic by any means so forgive if im wasting your time..but before you hunt into the hub and all that. try opening the hood and operating the carb manually while the trucks running and look for noise coming from any of your pulleys. fan belt,fan clutch,air pump,fan pulley or otherwise..also make sure its not comin from the dash..could be the odometer cable wearing out..just a thought. sounds like a sweet ride..good luck.
With regarding "phantom noises" the worst place to diagnose is from the drivers seat while driving.

GET A FRIEND THAT CAN DRIVE THE BEAST AND Oops, and let him drive around the neighbor hood or a big parking lot,
while you listen around the truck while you companero drives. If you are nimble it will be easy.

Trust me, you will do a better job of listening than anyone else can.
Funny you post that, I just did that, and I can narrow it down to in front of the tc...lots of searching left...
Front drive shaft U joints? Remove the front driveshaft and test drive it.

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